The present invention relates to a method for controlling the charging of multi-cell batteries, for example NiCd cells, in which the battery is coupled to a battery charger for passing a current through the battery.
Various types of principles are known in the art for charging batteries having, for example, NiCd cells. Examples of this are constant current charging, constant voltage charging, pressure and temperature charging, and pulse charging. The major advantage inherent in constant current charging is that the charger may be of extremely simple design, while its drawback is a restriction to a temperature range of between 0.degree. and 40.degree. C. This type of charger has an extremely long charging time at low temperatures, since the permitted mean current in cold conditions is considerably lower than at room temperature. Furthermore, the charging takes place in a completely uncontrolled manner, without any correspondence whatever to the capacity of the cells to accept the charging energy. Constant voltage charging is also uncontrolled, but in this process somewhat better use is made of the properties of the cell, but also charging time will be long, in particular at low temperatures. Because of the difficulties involved in providing pressure or temperature sensing elements, pressure and temperature charging occurs only in extremely special and rare circumstances. The reason for this is that, in this particular case, the practical difficulties are almost insurmountable. In conventional pulse charging, the charging is effected in cycles of, for example 1 Hz, the charging current being, for instance, twice as large as the discharging current. Pulse charging has proved to be more efficient than many other charging concepts, in particular at low temperatures. In conventional pulse charging, the only compensation is for poor regulation of the charging current of the battery. However, conventional pulse charging involves considerable charging times and relatively poor control of the various parameters.